1. Field of the Invention
The present invention relates to a level detecting device of bottom reference type in a plastic fuel tank for a motor vehicle.
2. Description of the Prior Art
In a level detecting device in a fuel tank for a motor vehicle, there has hitherto been developed (see the official gazette of the Japanese for Utility Model Registration Application Laid-open No. 193421/1985) a level detecting device of bottom reference type having a structure wherein a reference rod (a position setting arm) is secured integrally with a body by which the float arm of a float lying on a fuel surface is supported so as to be rotatable in a predetermined angular range. The body is supported by a spring and mounted on the fuel tank in the state of which the lower part of the reference rod abuts on the bottom of the fuel tank. The lower part of the reference rod presses the fuel tank bottom by virtue of a spring force, thereby intending to normally detect the height (level) of the fuel surface with reference to the fuel tank bottom on which the lower part of the reference rod abuts.
In recent years, plastic fuel tanks for motor vehicles have come into use. In general, the plastic fuel tank is mounted on the body of the vehicle by bands (usually, two bands) which are commonly made of steel.
With such a plastic fuel tank, the bottom thereof is secularly bulged and deformed by the fuel etc. contained therein. Therefore, when a level detecting device of the bottom reference type is applied to this tank, the reference point changes secularly. Also, the tank bottom is deformed by a stress ascribable to the structure in which the lower part of the reference rod is urged against the tank bottom by the spring. These disadvantages incur the problem that a stable performance of level detection is difficult to attain.